These studies will assess the growth and nutritional status of children with sickle cell disease (SCD) and will examine the interaction of these parameters with clinical status. Although the growth deficits of SCD patients have been previously described, the longitudinal course of their growth failure and its relationship to nutritional and disease-related factors is not understood. Poor appetite is frequently reported by mothers of SCD patients but the nutritional intakes of SCD patients have not been well documented. Furthermore, the energy cost of SCD has never been assessed. In this study, we will: (1) evaluate longitudinally the growth, nutritional status, and body composition of 200 SCD patients; (2) assess resting and total energy expenditure of SCD patients in a healthy state and during an acute SCD complication; and (3) determine the dietary intakes and nutritional needs of children with SCD. We hypothesize that deficits in height and weight, and delayed skeletal and sexual maturation result from three factors: 1) the effects of increased energy demand in the steady state; 2) the additional energy demand of acute vasoocclusive complications; and 3) low nutritional intake associated with poor appetite. The findings of these studies will provide guidelines for the nutritional needs of patients with SCD and determine the degree to which nutritional intervention can improve the growth and positively affect the clinical course of SCD.